cats

under what conditions will shifting cultivation be considered sustainable???

Raelle

only when the fallowing period is sufficient for the jungle to recover the lost nutrient for the next cultivation period, shift cultivation will be considered as sustainable

around 30 years

agricultural activities will speed up the lose of soil nutrient
lost of canopt cover
lost of litter from biomass
lost of wet and warm condition -> lost of decomposer -> no input of nutrient into the soil -> decrease soil fertility
crops will uptake soil nutrients which will not return back to soil

Raelle

30 years of fallowing can recover lost nutrient
growth of plantation is no longer disrupted by human activities
plant density recovered
ecosystem recovered
nutrient regernerated

30 years later cultivation again and fallow again
nutrient level can reach back to the original level
sustainable

cats

thank you
but other than the factor about fallowing period, any other factors as well?

dogwowo

1.  Government's population policy [Implement family control]
In some rainforest countries, their traditional idea is: born as many children as they can
If government can tackle this problem effectively, than the country will have less people.
As a result, the fallow period of shifting cultivation can last longer.


2.  Migration policy

If there have too many people in the urban areas, the government may encourage their people to move into the rainforests in order to lessen the over-population problem in urbans. Thus as mention in Point 1, if there have less people, then less people move into rainforests, the fallow period can last longer too.

3.  Better 'slash-and-burn' method

If the shifting cultivators adopt a better method, than the fellow period may last shorter.

[ 本帖最後由 dogwowo 於 2012-3-12 08:34 PM 編輯 ]

goobeee

in my point of view, the original shifting cultivation is sustainable (but only recent decades becomes not sustaintable)

1. It is extensive and non-sedentary
-->As the soil in TRF is infertile (due to heavy leaching) -->low land carrying capacity. Thus to be sustainble, extensive farming (i.e. low input / land) + long fallowing period is given after culitvation (i.e. shifting) -->soil nutrient recharged

2. small scale and subsistance farming
-->Shifting cultvation = traditional farming practice -->used primitive tool to clear small plot of land only, Thus, big trees keeps standing to provide humus + root to hold soil -->small scale devegetation is easier to recharged its nutrient -->sustainable

3. Polyculture
-->diversifed the crops grown -->with different growing period and absorb different types of nutrient --> so it wont left the land barren (avoid intensifying leaching and soil erosion) +avoid  imbalance soil nutrient storage -->sustainable

However, in recent decades, shifting cultivation is regarded as not sustainable.
1. Rapid population growth -->increaseing food demand + land for accomodation -->shortern fallowing period -->lowering land carrying capacity -->soil degradation -->fail to recharge to its climax i.e. adverse ecological succesion =secondary forest

NOTE: the 2nd part should be provide brief describtion is alright, as the question is asking when shifting cultivation considered as sustainable

cats

good^^